Other areas of the stock market, where profits are more dependent on the strength of the economy, lagged behind. Financial stocks in the S&P 500 fell 0.1 per cent. The Russell 2000 index of smaller companies rose just 0.5 per cent.
The 10-year Treasury yield swung from 0.88 per cent late Tuesday up to 0.94 per cent as polls were closing. It then sank as odds for a Democratic takeover of the Senate diminished and after Trump made premature claims of victories in several key states. It sat at 0.76 per cent an hour after trading opened on Wall Street.
"Both candidates at this stage often claim victory, but it's rare that we see an invocation of the court system at this point, and we expect quite a lot of market volatility," Rick Lacaille, global chief investment officer at State Street Global Advisors, said in a statement. "Basically, we are seeing a nightmare situation come true because now we are talking about legal battles," said Naeem Aslam, analyst at Avatrade.com.
"The market hates uncertainty and if we have continued uncertainty, then we're going to see prices fall, we're going to see volatility remaining high," said Kiran Ganesh, analyst at UBS bank.